Inhibiting scale with amino-phosphonic-sulfonic acids

ABSTRACT

This invention relates to compounds characterized by the presence of N-methyl, or substituted methyl, phosphonic acid and N-propylenesulfonic acid groups. These compounds contain at least one or more of each group and are bonded to the same or different amino groups. They are derived by reacting an amine with both propane sultone and with a carbonyl compound, such as formaldehyde, and phosphorous acid or its equivalent. 
     They have a wide variety of uses, for example as scale and corrosion inhibitors, chelating agents, etc.

This application is a Division of Application Ser. No. 442,778 filedFeb. 15, 1974, now U.S. Pat. No. 4,085,134.

The compounds of this invention may be presented by the followingidealized formula ##STR1## where N is an amino moiety and n and m are atleast 1, such as 1-5, for example from 1-3, but preferably 1.

In the case of a monoamine, n and m are 1. In the case of polyamine nand m can vary widely depending on the number of amino groups.Theoretically, the sum of n+m can be equal to the number of replacedamino hydrogens. In general, the sulfonic acid groups are 1-2 or moreand the phosphonic acid groups are 1-5 or more.

Any amine capable of reacting with propane sultone can be employed forexample any amine having at least one primary amino group. Where theamine has more than one primary amino group, the number of sulfonic acidgroups in the product will depend on the moles of sultone employed, forexample ##STR2##

Theoretically, some or all of the remaining nitrogen-bonded hydrogenscan be converted to the methyl phosphonic acid depending on thestoichiometry of the reactants.

Any amino group having a reactive N-hydrogen group which is capable ofreacting with a carbonyl compound and phosphorous acid or equivalent canbe reacted to yield the compounds of this invention.

The aminomethyl phosphonic acids of this invention and their salts maybe prepared by various methods. One method comprises reacting (1) anamine having reactive hydrogens attached to a nitrogen atom (2) acarbonyl compound such as an aldehyde or a ketone and (3) phosphorousacid, usually in the form of the dialkyl phosphite. The freeN-aminomethyl phosphonic acids and their salts may be prepared byhydrolysis of the phosphonic ester under acid conditions such as withstrong mineral acid such as HCl and the like.

These may be illustrated by the following reaction: ##STR3##

In the above equation X and Y are hydrogen or a substituted group suchas an alkyl or aryl group, etc.

Phosphonic esters are converted to phosphonic acids or salts thereofaccording to the following reaction ##STR4## and other correspondingreactions.

Salts of these can also be prepared, for example salts containing metal,ammonium, amine, etc. groups such as sodium, potassium, triethanolamine,diethanolamine.

A second method comprises reacting (1) an amine (2) a carbonyl compoundsuch as aldehyde or a ketone and (3) phosphorous acid preferably inpresence of a strong mineral acid such as hydrochloric acid. This methodyields the aminomethyl phosphonic acids directly.

This may be illustrated by the following reaction: ##STR5##

The general synthetic procedure involves two steps: (a) Reaction of aprimary amine with propane sultone to form a γ-amino sulfonic acid and(b) reaction of this molecule with formaldehyde and phosphorous acid.##STR6##

This reaction is applicable to a wide range of amines; thus R can bealkyl such as CH₃, C₂ H₅, C₃ H₇, C₄ H₉, C₆ H₁₃, C₈ H₁₇, C₁₂ H₂₅, C₁₈H₃₇, etc., straight chained or branched such as isopropyl, 2-ethylhexyl, etc., cyclic aliphatic groups such as cyclopentyl, cyclohexyl.

Other amines which can be reacted include polyamines such aspolyalkylene polyamines for example of the formula ##STR7## where A isalkylene for example having 2-10 carbons or more and n=1 to 10 or more,for example diamines such as ethylene diamine, propylene diamine,diethylene triamine, N-substituted 1,3,-propylene diamines, etc.

Amines suitable for this process include the following:

n-Butyl amine

2-ethyl hexyl amine

Monoisopropanolamine

Hexylamine

Heptylamine

Octylamine

Decylamine

Furfurylamine

Dodecylamine

Monoethanolamine

n-Amylamine

Sec-amylamine

2-amino-4-methylpentane

4-amino-2-butanol

5-isopropylamino-1-pentanol

Also, high molecular weight aliphatic amines known as Armeen 10, Armeen16D, Armeen HTD, Armeen 18D, and Armeen CD can be used (RNH₂).

Other amines include:

2-amino-2-methyl propanol

2-amino-2-methyl-1,3-propanediol

2-amino-2-ethyl-1,3-propanediol

3-amino-2-methyl-1-propanol

2-amino-1-butanol

3-amino-2,2-dimethyl-1-propanol

2-amino-2,3-dimethyl-1-propanol

2,2-diethyl-2-amino ethanol

2,2-dimethyl-2-amino ethanol

3-amino-1,2-butanediol

4-amino-1,2-butanediol

2-amino-1,3-butanediol

4-amino-1,3-butanediol

2-amino-1,4-butanediol

3-amino-1,4-butanediol

1-amino-2,3-butanediol

Amines having ring structures include cyclohexylamine, and variouscomparable amines with alkyl substituents in the ring.

A wide variety of polyamines also can be employed. These include thepolyalkylene polyamines such as of the formula: ##STR8## in which R" ishydrogen, alkyl, cycloalkyl, aryl, or aralkyl and R' is a divalentradical such as: ##STR9##

Examples of suitable polyamines include:

Ethylenediamine

Diethylenetriamine

Triethylenetetramine

Tetraethylenepentamine

Propylenediamine

Dipropylenetriamine

Tripropylenetetramine

Butylenediamine

Aminoethylpropylenediamine

Aminoethylbutylenediamine ##STR10##

Other polyamines in which the nitrogen atoms are separated by a carbonatom chain having 4 or more carbon atoms include the following:Tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, etc.

If desired, one can prepare a variety of reactants having two or moreamino groups and at least one hydroxyl group. One may use modificationsof procedures or the procedures themselves as described in U.S. Pat.Nos. 2,046,720, dated July 7, 1936, to Bottoms; 2,048,990 dated July 28,1936, to Britton et al.; 2,447,821 dated Aug. 24, 1949, to Sankus; and1,985,885 dated Jan. 1, 1935, to Bottoms. Examples include thefollowing: ##STR11##

Other suitable amines are exemplified by ethylenebisoxypropylamine,##STR12##

Another example of polyamines which may be employed as a reactant is thekind described as "Duomeens."

Duomeen is a trademark designation for certain diamines. Duomeen has thefollowing general formula: ##STR13## R is an alkyl group derived from afatty acid or from the mixed fatty acids as obtained from certain oils.The specific Duomeen and the source of the radical R are as follows:

Duomeen 12, R=lauric

Duomeen C, R=Coconut oil fatty acid

Similarly, a comparable diamine, presumably obtained from Rosin Amine Dand acrylonitrile, can be prepared. The structure of Rosine Amine D isas follows: ##STR14##

Polyamines from monoamines and cyclic imines, such as ethylene imine.##STR15##

It is to be noted that all the above examples show high molal groups,i.e., 8 carbon atoms or more. The same derivatives in which methyl,ethyl, propyl, butyl, amyl, hexyl groups, or the like, appear instead ofoctyl, decyl, etc., are equally satisfactory.

Cyclic amidines, such as imidazolines and tetrahydropyrimidines, havingan amino side chain can be reacted, for example: ##STR16##

Tetrahydropyrimidines from monocarboxylic acids andtrimethylenepolyamines. ##STR17##

Reaction conditions for step (a). The reaction between amines andpropane sultone is very facile and occurs quite readily at temperaturesfrom 30°-70° in a solvent such as methanol. Step (b) takes place at lowpH and is most conveniently performed in aqueous HCl. Thus the aminosulfonate and phosphorous acid are heated in hydrochloric acid duringthe addition of formaldehyde usually at reflux.

The following examples illustrate the procedures:

EXAMPLE 1

Propane sultone (61 g, 0.5 mole) was added in 5 mins. to a solution ofcyclohexylamine (50 g; 0.5 mole) in methanol (200 ml) at roomtemperature. After completion of the addition the reaction temperaturerose to 50° and was maintained at this temperature by slight cooling. Awhite solid rapidly separated and after a further 4 hr. stirring thereaction mixture was filtered. The white solid was collected, 102 g(92%), mp<300° identified as 3-cyclohexylamino propylsulfonic acid.

Analysis, calculated for C₉ H₁₉ NO₃ S, N, 6.34%, S, 14.47%: Found: N,6.30%, S, 13.8%.

3-Cyclohexlamino propylsulfonic acid (50 g; 0.23 mole) and phosphorousacid (18.5 g; 0.23 mole) were dissolved in a mixture of water (25 ml)and hydrochloric acid (25 ml) and heated to 100° (gentle reflux). Tothis solution was added 37% aqueous formaldehyde (28 g.; 0.34 mole)dropwise in 70 min. at 100°-102°. Heating at reflux was continued for afurther 3 hr. Evaporation of the aqueous acid gave a quantitative yieldof phosphonic sulfonic acid as a viscous gum. This gum was crystallizedfrom ethanol to yield pure product mp 192°-5°.

Analysis, calculated for C₁₀ H₂₂ NO₆ PS: N, 4.65%, P, 9.85%, S, 10.15%:Found: N, 4.59%, P, 9.12%, S, 10.6%. This data, together with NMRspectra confirm the structure as follows: ##STR18## (as a zwitterion).

EXAMPLE 2

Propanesultone (61 g; 0.5 mole) was added to a stirred solution ofn-butylamine (36.5 g; 0.5 mole) in methanol (200 ml) in 10 min. Thereaction temperature was kept at 50°-55° by cooling. After stirring 40min, a white solid began to separate. After stirring overnightfiltration yielded 3-butylaminopropylsulfonic acid 94 g (96%).

A solution of this aminosulfonic acid (40 g; 0.2 mole) and phosphorousacid (16.8 g; 0.2 mole) in 18% HCl (50 ml) was heated at reflux while37% formaldehyde (25 g; 0.3 mole) was added dropwise during 1 hr. Thereaction was completed by heating a further 3 hours at reflux to yieldthe sulfonic/phosphonic acid as a clear viscous gum upon removal ofsolvent. The product is represented by the structure: ##STR19##

EXAMPLE 3

In the manner of previous Examples n-hexylamine was reacted withpropanesultone to yield the 3-hexylamino propylsulfonic acid, mp

Analysis, calculated N, 6.27%, S, 14.35%: Found; N, 6.02%, S, 14.55.

3-Hexylamino propylsulfonic acid (0.49 mole) was reacted withphosphorous acid (0.49 mole) and formaldehyde (0.50 mole) in presence ofhydrochloric acid (100 ml) and water (100 ml). The crystalline productobtained from aqueous ethanol, mp 144°-7°, 79 g was the purephosphonicsulfonic acid of the following formula: ##STR20##

Analysis, Calculated: N, 4.42; P, 9.78; S, 10.10%: Found: N, 4.34; P,9.79; S, 10.37%.

EXAMPLE 4

n-Octylamine was converted into the expected octylaminopropylsulfonicacid by reaction with propanesultone in methanol.

Anaylsis; Calculated: N, 5.58; S, 12.75%: Found: N, 5.35; S, 12.19%.

This sulfonic acid (0.2 mole) was reacted with phosphorous acid (0.2mole) and formaldehyde (0.2 mole) as in previous examples.Crystallization gave the pure sulfonic-phosphonic acid mp 143°-5°, 39.3g.

Analysis- Calculated: N, 4.06; P, 8.97; S, 9.26%: Found: N, 4.23; P,8.50; S, 10.2%. In a similar manner the following compounds wereprepared:

    ______________________________________                                         ##STR21##                                                                    Analysis                                                                                Found       Calculated                                              Example R       N      S     P    N     S     P                               ______________________________________                                        Example 5                                                                             C.sub.12 H.sub.25                                                                     3.31   7.81  7.92 3.49  7.98  7.73                            Example 6                                                                             C.sub.16 H.sub.33                                                                     2.90   6.52  6.60 3.06  7.00  6.78                            Example 7                                                                             C.sub.18 H.sub.37                                                                     2.41   6.30  6.21 2.89  6.54  6.39                            ______________________________________                                    

The following examples illustrate the reactions of polyamines:

EXAMPLE 8

To a solution of ethylene diamine (30 g; 0.5 mole) in methanol (200 ml)was added propane sultone (61 g; 0.5 mole) during 15 mins. with slightcooling. After stirring overnight at ambient-temperature the solvent wasremoved to yield a viscous gum. NMR spectrum was consistent with theexpected structure:

    NH.sub.2 -CH.sub.2 CH.sub.2 NH-CH.sub.2 CH.sub.2 CH.sub.2 SO.sub.3 H

Analysis: Found, S, 17.57%: Calculated S, 17.58%.

EXAMPLE 9

In a similar manner to Example 8 ethylene diamine yielded a disulfonicacid, mp 259°-61°.

Analysis: Found, N, 9.11; S, 21.5%. Calculated, N, 9.20; S, 21.0%. Theproduct is mainly ##STR22##

EXAMPLE 10

The amino sulfonic acid of Example 8 (0.1 mole) was dissolved in amixture of hydrochloric acid (20 ml), water (20 ml) and phosphorous acid(8.2 g; 0.1 mole). The mixture was heated to 100° and aqueousformaldehyde (0.1 mole) was added during 50 mins. Heating was continuedfor 4 hrs. at which time aqueous acid was removed in vacuo. The residuewas crystallized from aqueous ethanol to yield white crystals mp 156°-8°C. The product is minaly ##STR23##

EXAMPLE 11

The amino propyl sulfonic acid of Example 9 (0.2 mole) was dissolved ina mixture of hydrochloric acid (40 ml), water (40 ml) and phosphorousacid (0.4 mole). Upon heating to 100° 40% aqueous formaldehyde (0.4mole) was added during 1 hr. The reaction was completed by heating at100°-102° for 4 hrs. Evaporation of the aqueous acid yielded the productas a gum. The structure is mainly: ##STR24##

EXAMPLE 12

To a solution of diethylene triamine (0.5 mole) in methanol (200 ml) wasadded propane sultone (0.5 mole) during 10 mins. Upon completion of theaddition the temperature rose to 70°. After the temperature of thesolution subsided to 30° the methanol was removed to yield a partiallycrystalline syrupy mass. NMR spectrum indicated that the product was amixture with main components.

(A) NH₂ (CH₂)₂ NH(CH₂)₂ NH(CH₂)₃ SO₃ H ##STR25## (A) was the majorcomponent.

EXAMPLE 13

By the procedure of Example 12 diethylene triamine (0.25 mole) wasreacted with propane sultone (0.5 mole). The product was a viscous gumwhose NMR spectrum indicated the structure to be as follows: ##STR26##

Analysis Calculated: N, 12.1%, S, 18.45% Found: N, 11.33%, S, 18.23%

EXAMPLE 14

The amino propyl sulfonic acid of Example 12 (0.5 mole) was dissolved ina mixture of hydrochloric acid (200 ml) water (200 ml) and phosphorousacid (2.0 mole) and heated at 100° C. To this solution was added 40%aqueous formaldehyde (2.1 mole) during 75 mins. The reaction wascompleted by heating at gentle reflux for 3 hr. The product issubstantially: ##STR27## with some product from isomer B.

EXAMPLE 15

The aminopropylsulfonic acid of Example 13 (0.24 mole) was dissolved ina mixture of hydrochloric acid (150 ml), water (150 ml) and phosphorousacid (0.72 mole) and heated to 100° C. At this temperature 40% aqueousformaldehyde (0.75 mole) was added in 1 hr. and the reaction completedby heating for 3 hours. Evaporation of the aqueous acid yielded thesulfonic/phosphonic acid. The main component is: ##STR28##

USE AS SCALE INHIBITOR

Most commercial water contains alkaline earth metal cations, such ascalcium, barium, magnesium, etc., and anions such as bicarbonate,carbonate, sulfate, oxalate, phosphate, silicate, fluoride, etc. Whencombinations of these anions and cations are present in concentrationswhich exceed the solubility of their reaction products, precipitatesform until their product solubility concentrations are no longerexceeded. For example, when the concentrations of calcium ion andcarbonate ion exceed the solubility of the calcium carbonate reactionproduct, a solid phase of calcium carbonate will form as a precipitate.

Solubility product concentrations are exceeded for various reasons, suchas evaporation of the water phase, change in pH, pressure ortemperature, and the introduction of additional ions which can forminsoluble compounds with the ions already present in the solution.

As these reaction products precipitate on the surfaces of thewater-carrying system, they form scale. The scale prevents effectiveheat transfer, interferes with fluid flow, facilitates corrosiveprocesses, and harbors bacteria. Scale is an expensive problem in manyindustrial water systems, causing delays and shutdowns for cleaning andremoval.

Scale-forming compounds can be prevented from precipitating byinactivating their cations with chelating of sequestering agents, sothat the solubility of their reaction products is not exceeded.Generally, this approach requires many times as much chelating orsequestering agent as cation present, and the use of large amounts oftreating agent is seldom desirable or economical.

More than twenty-five years ago it was discovered that certain inorganicpolyphosphates would prevent such precipitation when added in amountsfar less than the concentrations needed for sequestering or chelating.See, for example, Hatch and Rice, "Industrial Engineering Chemistry,"vol. 31, p. 51, at 53; Reitemeier and Buchrer, "Journal of PhysicalChemistry," vol. 44, No. 5, p. 535 at 536 (May 1940); Fink andRichardson U.S. Pat. No. 2,358,222; and Hatch U.S. Pat. No. 2,539,305.When a precipitation inhibitor is present in a potentially scale-formingsystem at a markedly lower concentration than that required forsequestering the scale forming cation, it is said to be present in"threshold" amounts. Generally, sequestering takes place at a weightratio of threshold active compound to scale-forming cation component ofgreater than about ten to one, and threshold inhibition generally takesplace at a weight ratio of threshold active compound to scale-formingcation component of less than about 0.5 to 1.

The "threshold" concentration range can be demonstrated in the followingmanner. When a typical scale-forming solution containing the cation of arelatively insoluble compound is added to a solution containing theanion of the relatively insoluble compound and a very small amount of athreshold active inhibitor, the relatively insoluble compound will notprecipitate even when its normal equilibrium concentration has beenexceeded. If more of the threshold active compound is added, aconcentration is reached where turbidity or a precipitate of uncertaincomposition results. As still more of the threshold active compound isadded, the solution again becomes clear. This is due to the fact thatthreshold active compounds in high concentrations also act assequestering agents, although sequestering agents are not necessarily"threshold" compounds. Thus, there is an intermediate zone between thehigh concentrations at which they act as threshold inhibitors.Therefore, one could also define "threshold" concentrations as allconcentrations of threshold active compounds below that concentration atwhich this turbid zone or precipitate is formed. Generally the thresholdactive compound will be used in a weight ratio of the compound to thecation component of the scale-forming salts which does not exceed about1.

The polyphosphates are generally effective threshold inhibitors for manyscale-forming compounds at temperatures below 100° F. But afterprolonged periods at higher temperatures, they lose some of theireffectiveness. Moreover, in an acid solution, they revert to ineffectiveor less effective compounds.

A compound that has sequestering powers does not predictably havethreshold inhibiting properties. For example, ethylenediamine tetraceticacid salts are powerful sequesterants but have no threshold activities.

We have now discovered a process for inhibiting scale such as calcium,barium and magnesium carbonate, sulfate, silicate, etc., scale whichcomprises employing threshold amounts of the compositions of thisinvention.

In general it is preferred that at least 50% but preferably at least 80%of the nitrogen-bonded hydrogens of the polyamine be replaced bysulfonate or phosphonate groups.

Scale formation from aqueous solutions containing an oxide variety ofscale forming compounds, such as calcium, barium and magnesiumcarbonate, sulfate, silicate, oxalates, phosphates, hydroxides,fluorides and the like are inhibited by the use of threshold amounts ofthe compositions of this invention which are effective in small amounts,such as less than 100 ppm and are preferably used in concentrations ofless than 25 ppm.

The compounds of the present invention (e.g., the acid form of thecompounds) may be readily converted into the corresponding alkali metal,ammonium or alkaline earth metal salts by replacing at least half of thehydrogen ions in the phosphonic acid group with the appropriate ions,such as the potassium ion or ammonium or with alkaline earth metal ionswhich may be converted into the corresponding sodium salt by theaddition of sodium hydroxide. If the pH of the amine compound isadjusted to 7.0 by the addition of caustic soda, about one half ofthe--OH radicals on the phosphorous atoms will be converted into thesodium salt form.

The scale inhibitors of the present invention illustrate improvedinhibiting effect at high temperatures when compared to prior artcompounds. The compounds of the present invention will inhibit thedeposition of scale-forming alkaline earth metal compounds on a surfacein contact with aqueous solution of the alkaline earth metal compoundsover a wide temperature range. Generally, the temperatures of theaqueous solution will be at least 40° F., although significantly lowertemperatures will often be encountered. The preferred temperature rangefor inhibition of scale deposition is from about 130° to about 350° F.The aqueous solutions or brines requiring treatment generally containabout 50 ppm to about 50,000 ppm of scale-forming salts. The compoundsof the present invention effectively inhibit scale formation whenpresent in an amount of from 0.1 to about 100 ppm, and preferably 0.2 to25 ppm wherein the amounts of the inhibitor are based upon the totalaqueous system. There does not appear to be a concentration below whichthe compounds of the present invention are totally ineffective. A verysmall amount of the scale inhibitor is effective to a correspondinglylimited degree, and the threshold effect is obtained with less than 0.1ppm. There is no reason to believe that this is the minimum effectiveconcentration. The scale inhibitors of the present invention areeffective in both brine, such as sea water, and acid solutions.

Calcium Scale Inhibition Test

The procedure utilized to determine the effectiveness of scaleinhibitors in regard to calcium scale is as follows:

Several 50 ml. samples of a 0.04 sodium bicarbonate solution are placedin 100 ml. bottles. To these solutions is added the inhibitor in variousknown concentrations. 50 ml. samples of a 0.02 M CaCl₂ solution are thenadded.

A total hardness determination is then made on the 50--50 mixtureutilizing the well known Schwarzenbach titration. The samples are placedin a water bath and heated at 180° F. 10 ml. samples are taken from eachbottle at 2 and 4 hour periods. These samples are filtered throughmillipore filters and the total hardness of the filtrates are determinedby titration. ##EQU1##

    ______________________________________                                        Calcium Scale Inhibition                                                      Compound     Concentration  % Inhibition                                      ______________________________________                                        Example 1    100 ppm        86%                                               Example 4    100 ppm        24%                                               Example 4    200 ppm        60%                                               Example 11    50 ppm        95%                                               Example 11   100 ppm        100%                                              Example 14    10 ppm        66%                                               Example 14   100 ppm        100%                                              Example 15    10 ppm        42%                                               Example 15    50 ppm        95%                                               ______________________________________                                    

We claim:
 1. A process of inhibiting scale formations in a system inwhich there is present water containing scale forming compounds whichcomprises treating the water with an amount effective to diminish scaleformation of a compound which is an amine containing the followingnitrogen-bonded groups:

    --(CH.sub.2).sub.3 SO.sub.3 M and ##STR29## wherein R and R' are hydrogen or an alkyl or aryl group and M is hydrogen or a salt moiety, the nitrogen to which the groups are bonded being amino nitrogen of the amine, the salt moiety being an alkali metal, an alkaline earth metal, ammonium or ammonium form of an amine, the compound in acid form having the

    --(CH.sub.2).sub.3 SO.sub.3 H and ##STR30## as the sole acidic groups, the compound with hydrogen in place of said groups being an amine in which said nitrogen is amino nitrogen.


2. The process of claim 1 wherein the water is treated with a thresholdamount of the compound and all of the scale forming compounds are insolution.
 3. The process of claim 1 where the --(CH₂)₃ SO₃ M and##STR31## groups in the compound are bonded to the same nitrogen atom.4. The process of claim 3 where the compound has the formula ##STR32##where R is a hydrocarbon group.
 5. The process of claim 1 where thecompound has at least 2 nitrogen atoms.
 6. The process of claim 5 wherethe compound has the formula ##STR33## where n=1-4, where the nitrogenvalences are joined to hydrogen, --(CH₂)₃ SO₃ M or ##STR34## with theproviso that that compound contain at least one --(CH₂)₃ SO₃ M and atleast one ##STR35## and where A is alkylene.
 7. The process of claim 6where the compound contains no nitrogen-bonded hydrogens.
 8. The processof claim 6 where in at least one instance the --(CH₂)₃ SO₃ M and##STR36## groups of the compound are bonded to the same nitrogen.
 9. Theprocess of claim 8 where the compound is derived from ethylene diamineor diethylene triamine.
 10. The process of claim 9 where the compoundhas the formula ##STR37##
 11. The process of claim 9 where the compoundhas the formula ##STR38##